Coded signaling system



July 4, 1944. c. E. STAPLES ETAL 2,352,743

i I CODED SIGNALING SYSTEM Filed July 14:,A 1945 '6 'C Fly.;

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INVENTORS CI'awFdE. Szaplef and E EYHePma/zloffen H- 'h/pp k- WHP vTHEIR ATTORNEY Patented July 4, 1944 -CDED SIGNALING SYSTEM Crawford E.Staples and 'Herman G. Blos'ser,v Pittsburgh, Pa., assignors to TheUnion Switch itv Signal Company, Swissvale, Pa., a tion of PennsylvaniaCorpora,-

`Application July 14, 1941i, SerialNo. 494,618

10 Claims.

, Our invention relates to signaling apparatus employing coded energy.`1 In Letters Patent of the United States No. 2,021,944 to Frank I-I.Nicholson there is. shown a signaling system in which master code istransmitted in one direction over a pair of conductors to operate a codefollowing relay and thereby perform selected functions at one end oftheconductors, while during the off periods in the master code feed-backenergy is transmitted in the other direction over these conductorstooperate a feedback relay and thereby perform selected functions at theother .end of theconductors.

It has heretofore been proposed to control the polarity of the feed-backenergy so that this energy is f normal polarity at times and is ofreverse polarity at other times, and to provide one feed-back relayresponsive toenergy of one polarity and another feed-back relayresponsive to energy of the other polarityso that the feedback energy.may be employed to perform two different functions.v The systems ofthis type heretofore suggested have employed feed-back detector relaysofthe polar biased neutral type, the contacts of which release when therelaywinding is deenergized, and which when released become picked upwhen and only when energy of a particular polarity is supplied to therelay.

vIt is preferred toemploy feedback detector relays of the polar sticktype for this purpose, and it is an object of this invention to providean improved system employing feed-back energy of both polarties andhaving feed-back detector relays of the polar stick type.

Another objectief thisk invention is to provide an improved system ofthe type described which is arranged so that the contacts ofboth of thefeed-back detector relays are moved to a selected oneof.theirvpositionsiwhen mastercode energy is supplied to the conductors,and so that the contacts of one-of the feed-back detector relays aremoved to their other position. by feed-back energy of one polarity, andso that the contacts of the other .one of thefeed-.back detector relaysare moved to their other position by feed-back energy of the otherpolarity," t A further object ofthe invention'is to provide Anotherobject of the invention is to provide a system incorporating codingmeans for revers-T ibly connectingv one of the feed-back ldetectorrelays'across the section rails and for supplying master code energy to'thesection rails in series with the rwindingsfof thefeed-back detectorrelays so that the master code energy moves the contacts of bothof the.feed-back detector relays to a selected position andso that thefeed-back detector relays respond to different polarities of feed-backenergy. i

A further object of the invention is to provide an improved system ofthe type described and incorporating meansy to ,delay reversal of theconnection of one of the feed-backrelays with the track rails for ashort period subsequent to interruption of the supply of master code tothe track circuit and thus enable energy stored in the track circuit as:a resultof the supply of master code energy to thetrack railsto be dis`sipated before connectiony of the feed-back relay with the track railsisreversed to thereby prevent operation of the feed-back relay by energystored in the track circuit. y

Other objects' of the invention and features of` novelty will beapparent from the following description taken in connection with theaccom-A panying description. y

We shall describe two forms of coded signaling apparatus embodying ourinvention, and shall then point out the novel features thereof inclaims. u

`In practicing o ur invention we provide two feed-back detector relaysof the stick polar type, while we employ two coding relays which arearranged so that when the contacts of both re' lays are picked up,master code energy is supplied to the rails of a section of railwaytrack, orother pair of conductors, over a circuit including in seriestherewith the windings of the feed-,- back'detector relays so vthat thecontacts of both feedback relays areI moved to a selected position bymaster code energysupplied through their windings. The coding relays arealso arranged so that one of these relays releases before the other andlso that the first one of the coding rean improved systemof. the typedescribed which isadapted to be applied to' the track circuit of asection of railway track andwhich is arranged so that energy stored inthe track circuit ,as a result of the supply o f master code energytothe section rails cannot falsely operate either feed-v backdetectorrelay.

lays to :release 4interrupts the supply of master code to the' sectionrails, while the other coding relay reversibly connects one of thefeed-back detector relays across "the section: rails so that bothfeed-back detector relays will respond in the same manner to master codebut will respond only to ldifferent polarities offeed-back energy. Theinterval between' release of the first vcoding relay to interrupt thesupply of master code energy to rails. In the system shown in Fig. 1when the coding relays are picked up, the detector relays are connectedin series across the section rails,

while in the system shown in Fig. 2 when thev coding relays are pickedup, the feed-back detector relays are connected in multiple across thesection rails.

In the drawing Fig. 1 is a diagram of a section of railway trackequipped with track circuit apparatus embodying our invention, and

Y Fig. 2 is a diagram showing a different arrangement of apparatus whichwe mayemploy.

Similar reference characters refer to similar parts in each of the twoviews.

Referring to Fig. 1 of the drawing, there is shown therein a stretch ofrailroad track having track rails I and 2 divided by insulated joints 3into track sections for signaling purposes. One

complete track section, designated 6T, together with portions of theadjoining sections 5T and 1T, is shown in the drawing.

The track circuit apparatus for section 6T is arranged so that mastercode of one frequency or another determined by occupancy of section 1Tis supplied to the section rails at the righthand end of the section,while feed-back energy of one polarity or the other determined byoccupancy of section 5T is supplied to the section rails atA theleft-hand end of the section.

The equipment at each end of the track section includes a source ofdirect current, such as a storage battery, notshown, the terminals ofwhich are designated B and C. v

The equipment is shown in the condition which it assumes when the trackstretch is vacant. At this time relay 'II-I, which is controlled bytraic in section 1T, is picked up, and relay EPC, which is governed bytraffic in-section 5T, is also picked up. The relays 'IHfand SPC may becontrolled in any appropriate manner. and in order to simplify thisdisclosure, the means for controlling these relays have not been shown.

As relay 'IH is picked up, its contact I0 estab lishes the circuitcontrolled by the contact of code transmitter IBGCT for supplying energyto coding relays SCTM and BCTMM and these relays. operate at the 180code frequency. On closing of the contact of code transmitter IBIiCTenergyv is supplied tothe winding of coding relay SCTM, and prior topicking up of the contacts of relay GCTM, is supplied over back contactI2 of relay ECTM to the winding of relay SCTMM, while on picking up ofrelay ECTM energy is supplied directly from the source to relay GCTMMBCTM and release of the contacts of relay ECTMM.

As explained below, the supply of energy from the track battery STB tothe rails of section 6T is cut off when relay GCTM releases, and asexplained in Letters Patent of the United States No. 2,285,891, issuedJune v9, 1942 to Herman G. Blosser, the interval between release ofrelay GCTM and release of relay SCTMM provides a period during whichenergy stored in the track circuit may be dissipated so that the relays6WD and GWH will not be operated by this energy.

When relays BCTM and SCTMM are both picked up, master code energy issupplied from track battery GTB to the track relay GTR over the circuitwhich is traced from the positive terminal of the battery over trackrail I, through the winding of track relay GTR, back contact I4 of relayGIR, track rail 2, winding of relay 6WD from left to right, frontcontact AI5 of relay ECTMM, winding of relay `IiWH from left to right,front contact I6 of relay'EC'I'MM, and front contact II of relay GCTM tothe negative terminal of the battery.

The energy supplied over this circuit picks up the contacts of the trackrelay GTR, while it causes the contacts o'f relays 6WD and GWH to moveto their normal position if they are'not already in that position.

On release `of the contacts of the code transmitter controlling thesupply of energy to the coding relays GCTM and GCTMM, the relay BCTMreleases and its contact I2 interrupts the circuit of relay GCTMM butthe operating` characteristics of the relay SCTMM are such that itscontacts remain picked up for a short period subsequent to release ofthe relay GCTM. I n addition, on release of relay BCTM its contact I1interrupts the circuit of the track battery GTB and establishesa'circuit to connect relays 6WD and BWH across the section rails as.long as relay GCTMM remains picked up. rWhen front point of contact I'Iof relay GCTM opens, the supply of energy from the battery GTB to thesectionrails is cut off, but because of the inductance ofthe trackcircuit, or of other conditions, energywlll continue to ow therein inthe same direction in which it had been owing, and energy may still beflowing in the track circuit when theA back point of contact I'I closes.If energy is owing in the track circuit when back point of contact IIcloses, this energy will flow from rail 2 through the winding of relay6WD from left to right, over front contact I5 of relay SCTMM, throughthe winding of relay GWH from left to right, and over front contact I6of relay GCTMM and back contact II of relayCTM to track rail L. Thedirection of flow of this energy through the windingsfof relays 6WD andBWH is such as to hold the contacts of these relays in theirAleft-handVor normal position, that is, in the position to which they .were movedby the supply of master code energy through the relay windings.

On release of the contacts of relay BCI'MM the connection of the relay IiWH across the section rails is reversed so the left-hand terminal ofthe winding of this relay is connected to track rail I and theVright-hand terminal of the winding of l this relay is connected throughthe winding of BC'I'M release, while there will be a short time relay6WD to track rail 2. If energy, resulting from inductance of the trackcircuit ory other condition should now ow from rail 2 to rail I throughthe windings of relays 6WD and EWH it would cause the contacts of relayGWH to move from their left-hand to their right-hand position.

time intervalbetween the instantat whi'chwsol'r-fv tact, H of relay BCTMreleases and." interrupts the circuit of the battery STB', and theinstant at which relay SCTMM releases to reverse con nection of` relayGWH .with the track rails, and this time interval is long enough topermit en'-Y .ergy' present in the track circuit as a result of. supplyof energy to -thei track circuit from the track battery to bedissipated. Accordingly, there isno possibility that'the relays 6WD andSWH will be operated yby energy stored in the track'circuit Y vOninterruption of the supply of energy'frorn .the track battery r STB tolthe1 sectiorr` rails the track relay SI'R releases, While onjrelease ofthe vvtrack vrelay contacts an impulse'of energy is supplied through thedecoding transformer GDTV to the relay STR, and yis of' the polarityeflective to pickJ up theV contacts of relayv SIR to thereby cause animpulse' of energytdbe supplied from battery SFB to the sectionfrailswhile disconnecting Vthe track relay from the'sectlon rails.v

vAn impulse of Yenergy was also supplied from the decoding transformerto the` relay GIR on picking up of the track relay contacts. However,the relay SIR'is of a type the contacts of which when released pick uponlyv when energy of a particular polarity is supplied `to the relaywind-- ing, and the various parts ofl` the 'apparatus are arranged sothat the `energy supplied to vrelay SIR on picking up of the tracklrelay contacts is of the wrong-polarity to` pick up the contactsof relaySIR.l

At' this time section 5TV is unoccupied so relay GPC is picked up andthe impulse of energy supplied from battery SFB `to the section rails isof normal polarity, and flows from the positive ter-v minalf of thebattery over 'front contact 20' of relay EPC, track rail I, back contactl5 of relay GCTMM, winding of relay BWHffrorn left tori'ght, backcontact I6 ofrelay SCTMM,'winding ofrelay SWDfrom right to left;k trackrail V2, front contact I4 of relay SIR, and front contact 2| of relaySPC to the negative terminal of thebattery SFB.

The impulseofenergy supplied from battery SFB to the section railslsends energy to relays ISWH` and'SWD in series, and as the impulse ofenergy is of? normal polarity, it vholds the contacts of-relay6WH1v vintheir 'normal position, while it causes# the 'contacts' of relay V6WD tomove to their right-hand or reverse position. i

After a short time interval the relay EIR re leases andv cuts offthesupply of energy 'from battery SFB` to the'sectionrails and connectstrack relay STR across'thevsection rails. During the next picked-upperiod of the' relays SCTMV the contacts of this=relay to move to theirlefthand or normal position, while the energy supvpliedv through thewinding of relayBWHfholds the relay contacts in their'normal position. j

On continuedsupply of master code to the'sec tion railsv the contactsvof relay SWD are returned to their normal position each timethatthelfeed-back-impulses is such that each impulse offeedeback energymoves the contacts of relay 6WD to their reverse position.

As a result of code following operation of track relay STR., energy issupplied through the decodingtransformer SDT tov relay 6H; while as thetrack relay is being operated by energy of 180 code frequency, energy issupplied through the resonant rectier unit I DU to relay 6D, and thecontacts of relays SH andi- SD are picked up and' establish the circuitofthe green or clear lamp G of signal SES which governs movement oftraffic from left to right through section BT. The 'resonant rectierunitI BDDU includes-a capacitance and an' inductance which are arranged andproportioned to pass sufficient en'- ergy to pick up the relay 6D whenand only when thetrack'relay' STR is operated at the 180 code rate,while the unit includes a rectifier for rectifying the energy 'supplied'through the unit.

As a result of movement of the contacts of relay 6WD between their twopositions, energy is supplied Vthrough the associated decoding trans#former to relay SWDP and its contact 23 is picked upto interruptthecircuitA of the lamps Y and R of signal SWS and to establish thecircuitof` the lamp G" of signal SWS which governs movement oft'raicfrom left to right in section 6T.

At this time the contacts of relay SWH remain inftheir left-hand ornormal positions so that energy is not supplied to relay SWHP and itscontact 24 remains released.

Operation-of equipment on movement of a train through the track stretchfrom. left to right When a train moving from leftr to right enterssection 5T, relay GPC' releases and changes the energy supplied frombattery SFB to the'sect'ion `rails from normal to reverse polarity. Onpicking up of relay SIR' at a time when relays CTM and `SGTMM arereleased, energy yflows `from the positive terminal of the'battery overVback contact 20 of relay SPC, front contact I4 of relay SIR, track rail'2, winding of relay SWD'from left to right, back contact IS of relaySCTMM, winding of relay SWI-l'from right to left, back contact l5 ofrelay .BCTMM, track rail I, and back contact 2l of relay E PC toy thenegati-ve terminal of the battery SFB". The direction of iiow offeed-back energy through the windings ofrelays 6WD and VISWH is suchthat the contacts of relay 6WD areheld in their lefthand orncrrnalposition, while the contacts of relay '5W-H are moved to theirright-hand or reverse position.

f On releasev of the contact of relay EIR the supply of energy from thebattery SFB to the sectionV rails is interrupted, and the track relaySTR'is connected across the Vsection rails,l while on picking up of therelays SCTM and GCTMM an impulse o f master code energy is supplied from'battery GTB to the section rails in series with the windings offvrelays BWH and 6WD. As explained above, the direction of .flow-of thisenergy through the windings of relays -WH and 5WDV is such as to holdthe relay contacts in their normal position; or tomove them to thatposition if they are not already in their normal position. Accordingly;the contactsof relay VSWH are moved `to ytheir normal position while'the contacts of relay 6WD areheld in their normal position,

Oncontinued operation of the equipmentthe contacts of relay EWI-l aremoved to their righthand'position by the feed-back energy 'and arereturned' to their left-hand position 'by the master code impulses,while the track relay tTR'. operates inthe Ausual manner to causeenergy'to "be sup-- plied through the transformer GDT to relays 6H and6D. As a result of movement of the contacts of relay BWI-I between theirtwo positions, energy s Ysupplied through the associated transformer to.relay BWHP and its contact 24 picks up, While asthe contacts of relay6WD remain in their normal positions, energy is no longer supplied torelay GWDP and its'contact 22 releases and interrupts the circuit of thegreen lamp Gf and establishes the circuit including front Contact 24 ofrelay GWHP for supplying energy to the yellowlamp Y'of signal EWS.Accordingly', when an eastboundtrain enters 'section 5T, signal BEScontinues to display its green or clear indication, while the polarityof the feed-back energy supplied over the rails of lsection 6T.ischanged so that relay EWDP releases and relay EWI-1P picks up tolthereby cause signal- SWS to display its yellow instead of its greenindication.

When the train moving from left to right enters section 6T, the trackrelay VSTR, isv shuntedand ceases to follow code so energy is no longersupplied to relays 6H and 6D and they release and cause signal BES todisplay'its red or stop indication. In addition, when track relay STRceases to follow coda-energy is no longer supplied'to relay SIR and itscontact remains released so that feed-back energy is no longer suppliedto the track rails and the contacts of relay EWI-I remain in theirnormal position and relay SWHP releases so that its contact 24interrupts the circuit of the yellow lamp Y and establishes the circuitof the red lamp R of signal EWS. p I

When the train vacates section T, relay SPC picks up so that onsubsequent operation of relay GIR the impulses of feed-back energysupplied to to. pick up the relay 5D. Accordingly, signal GESk nowdisplays its yellow or caution indication.

In addition, on operation of the 'track relay energy is supplied to therelay SIR and it oper- .ates to supply impulses of feed-back energy tothe section rails. As relay 6PC is picked up, the impulses .offeed-back., energy are vof. normal polarity and they loperate relay 6WDso that energyis supplied to relay 6WDP and its contact 23 picks up tointerrupt the circuit of the red lamp R and establish the circuit of thegreen lamp G of signal SWS.

--When the train vacates section 1T, relay 1H picks up and transferscontrol of coding relays liCTM and GCTMM to code transmitter I8OCT vsothat energy of 180 code frequency is supplied to the rails of sectionGT, and onV resultant operation of track relay GTR by energy of 180 codefrequencythe relay 6D picks up and interruptsthe circuit cf the yellowlamp Y and establishes the circuit of the green lamp G of signal BES.

Operation of equipment on movement of aA train I through, the trackstretch from. right to left When a train moving from right to leftenters section 1T, relay,Y 1H releases and changes the energy suppliedto section 6T from 180 Yto 75 code frequency and the rate of AoperationAof track relay GTR'is reduced so that'relay 6D releases and interruptsthe circuit of the green lamp G and establishes the circuit of theyellow lamp Y of signal BES. At this time relay GPC is picked up whilerelay GIR continues to operate and feed'- back energy of normal polarityis supplied'to the section rails and it causes relay EWDP to be pickedup so thesignal SWS displays its green indication.

When the train. advances into section 6T, the track 'relay GTR isshunte'd and ceases to follow code so relay 6H releases and causessignal BES to display lits red indication, while feed-back energy ceasesto be supplied to 'the section rails and relay 6WD ceases to operate andrelay 6WD? releases to cause signal SWS'todisplay itsfred indication. iI

When the train enters section releases so that on subsequent operationof relay GIR'the feed-back energy supplied'to the 'section-rails is ofreverse polarity- When the tran;vacates vrsection 1T,- relay 1 picks upso that coding relays GCTM and BCTMM operate at the cOderate', but aslong as section 6T is occupied, the track'relay remain's'released andfeed-back energy is not 'supplied over the section rails so that signalsEES and `SWS continue to display their stop indications.-

When the train vacates section 6T, the master code of 180 c'odefrequency supplied to the section rails operates the track relay GTR, sothat relays 6H and 6D pick up and cause signal GES to dis'- play itsgreen indication, While relay SIR is operated to supply feed-back energyto the track rails. As relay BPC is released, the feed-back energy is ofreverse polarity and operates relay 6WH so that relay IISWHP picks upand' causes signal SWS to display'itsyellow or'caution' in'- YMoamcation shown in Fig. l2 ofthe drawing in series therewith thewindings of' -thefrelaysV 6WD and SWH in series.

' In operation, when the -coding relays Y and BCTMM arerboth pickedup,energy is'sup- Y plied from the battery GTBover the circuit which istraced from the positive terminal of the battery to track rail l,through 'the winding of the track relay, not shown, over track rail'z,through winding of relay 6WD from left to right,V and also from rail 2over front contact 2150i relay GC'I'MM-"and throughwinding of relaySWH'in-multiple' with the windingl of relay 6WD,1ov'er front contact y2lof relay BCTMM and front contact -|1 ofr'relay BCTM to the negativeterminal ofthe 4battery I SIB. As master code energy supplied tothesecrrr,y relay tecV In Fig. 2 of the drawing there isfshownf modifiedarrangement of apparatuswliich we may tion rails'flows through thewindings of the relays 6WD and EWH from left to right, the contacts ofthese relays are moved to their left-hand or normal position, or areheld in that position if they are already in that position.

On release of the relays BCTM and BCTMM the supply of energy frombattery BTB to the section rails is cut off, While relays 6WD and GWHare connected in series across the track rails over the circuit which istracedfrom rail I over back Contact 21 of relay SCTMM, through windingof relay GWH from left to right, and through winding of relay 6WD fromrightto left. -1 l As the relays 6WD and GWH are connected across thesection rails when the relays -GCTM and QCTMM are released, feed-backenergy supplied to the section rails may flow through the windings ofrelays 6WD and BWI-l ,tol operate them. When the polarity of thefeed-back energy is such that the positive terminal of the feedbackbattery is connected to track `rail I, the direction of ow of feed-backenergy through the winding of relay 6WD is suchthat the contacts of thisrelay lare moved to their right-,hand or reverse position,while `thedirection of flow of energy through the winding of relay GWH is suchthat the contacts of this relay are held in their left-hand or normalposition.

Similarly, when the polarity of the feed-back energy is such that thepositive terminal of the feed-back battery is connected to. the track-rail 2, the direction of flow of energy through the winding of relay6WD is such that the `,contacts of this relay are held in theirleft-hand or normal position, while the direction of iiow of energythrough the winding of relay BWH is such that the contactsof this relayare moved to their reverse or right-hand position. r

On picking up of the contacts'of relaysGCTM and ECTMM master `codeenergy is againsupplied through the windings/of relays, 6WD and.6WH tothe section rails, and as explained above, this energy moves thecontacts of -relays BWI-I or. 6WD to their left-hand or normal position,or .holds them in that position if they are already in their normalposition.

Accordingly, the modification shoWninFig. 2 operates so that one or theother of therelays 6WD and BWH is operated by feed-back energy, the onedepending on the polarity of the feedback energy, while master codeenergy vsuppliedto the section rails vrestores to their normal positionthe contactsk of whichever vone of the relays BWH and 6WD that wasoperated by the feed-back energy. 1

As a result of operation of relay 6WD or SWH by feed-back energy. therelayV GWDP or.-6WHP is picked up and these relays may control a signal.in the manner explained in connection `with the system shown in Fig. l.

The modication shown in Fig. 2 also operates like that shown in Fig. 1toprevent false. operation of the feed-backdetector relays by energystored in the track circuit.

As pointedV out above, when the coding relays. BCTM and SCTMM are pickedup, the track battery BTB is connected across the section rails inseries with the windings of relays 6WD and GWH inV multiple. At thistime :the positive terminal of the battery is connected to ltrack railI, whilev the negative terminal of the battery is connected over frontcontact II of relay V.GC'I'M and frontV contact 2B of relay GCTMM to theright terminals of the windings of relays IiWzHV and 6WD so thisterminal of the vbattery is connected through the 75 g employed inotherways, as for exampleonaline Winding of relay 6WD .to .trackrail 2, andis also connected through Winding of relay GWHv and front contact 21 ofrelay GCTMM to track rail 2. Under Athese conditions, energy from thetrack battery flows. through the windings of relays 6WD and BWI-I fromleft to right andcauses the contacts of these relays to occupy theirlefthand or normal position.

On release of :the contacts of. relay SCTM its contact I2 interrupts thecircuit oi relay ECTMM, but .the contacts of relay BCTMM remain pickedup for. a short time interval. In addition, on release .of relay 16CTMits contact VI'I interrupts the circuit traced above for supplyingenergy from the track battery through the windings of relays 6WD andtWHto the track rails, and establishes a circuit to connect the relays 5WDand EWI-I across the track rails so that energy which continues to flowin the track circuit subsequent to interruption of the supply of energyfrom the track battery .will flow through .the windings ofrrelaysWDandBWH in the direction to maintain. their contacts in the normal position.

YAs pointed-out above, lprior to release of relay GCTM, the positiveterminal of the track battery is connected to track rail I, and energyfrom the track battery Hows through the windings of the relays 6WD and`GWH .from their left-hand to their right-hand terminals andthe relaycontacts are moved to their .left-hand or normal position.` When contactI'I of relay GCTM releases and interrupts .the circuit Yof the .trackbattery, energy in the track circuit due .to inductance of the trackcircuit or other conditions. continues to flow in the same directioninwhichv it had been flowing.V Accordingly, this energy news from trackrail 2 through the winding of relay 6WD from left vto right. )and overfront contact 23 of `relay BCTMM and back contact. 'Il' of relayr totrack rail I. In. addition, energy flows `from track rail 2 overirontcontact 2l of relay SGTMM. through winding of relay. EWI-I from left toright, and v over front .contact 28 of relay SQTMM and back contact I'Iof .relay BC'I'M to track rail I. Since energy 'stored in the trackcircuit hows through the windings of relays 6WD and BWH from leittoright, this energy holds the contacts of these yrelays in theirleft-hand or normal position.

After a short time interval the-relay. ECTMM releases and interrupts theabove traced circuit for connecting -relays 6WD and BWH in multipleacross the track rails and connects these relays in series across thetrack rails with the lefthand terminal of the winding oi relay BWHconnected tothe track rail I so that relays 6WD and -6WI-I areresponsive to dierent polarities of feed-back energy.

`As explained in connection with Fig. 1,..after release of relay BCTM:the relay BCTMM remains picked up for a period long `enough for .energycircuit. Likewise, While in the track circuits illustrated and describedthe feed-back energy is employed to govern a signal controlling movementof traffic in one direction through the track section, the feed-backenergy'is not limited to use for this purpose, and the feed-back energymay be employed to perform any appropriate functions.

Although we have herein illustrated and described only two forms ofsignaling apparatus embodying our invention, it is understood thatvarious changes and modications may be made therein within the scope ofthe appended claims without departing from the spirit and scope of ourinvention. Y Having thus described our invention, what we claim is:

l. In a coded signaling system, in combination, a pair of conductorsextending .between a rst and a second location, a iirst and asecondvpolarized detector relay at said rst location, a coding devicehaving contacts continuously actuated between a iirst anda secondposition, the contacts of said coding device being eiective when intheir rst position to connect a source of unidirectional energy acrosssaid. conductors through the windings of said detector relays so thatenergy supplied from saidlsource to the conductors movesl the contactsof `both detector .relays to their normal position,.the contacts of saidcoding device being effective when Vin their second position to connectsaid detector relays across said conductors in such manner that thecontacts of one of said relays are moved to their reverse position byenergy of one polarity and so that the contacts of the other of saidrelays are moved to their reverse position by energy of the otherpolarity, a coderfollowing relay at said second location-operated byenergy supplied oversaid conductors from said'rst location, means atsaid second location for supplying to said conductors during theintervals between the irnpulses of energy supplied to said conductors atthe rst location energy which at times is of one polarity and at othertimes .is ofv the other' polarity, signaling means governed by said codefollowing relay, and signaling means governed by said detector relays. Yv

.2. In a coded signaling system, in combination, a pair of conductorsextending between a rst and a second location, a first vand a secondpolarized detector relay at said iirst location, a coding device havingcontacts continuously actuatedv positions, the contacts of said codingdevice being effective when in their second position to connect saiddetector relays across said conductors insuchmanner that the contactsofone of said relays are moved to ltheir reverse position by energy ofone-polarity` supplied over said conductors and so that the contacts ofthe other of saidrelays are moved to their reverse position by energy ofthe other polarity supplied over saidconductors, a code following relayat -said second location operated by master code energy suppliedv oversaid conductors. means at saidY second location for supplying impulsesvofV feed-back energy to said conductors in the intervals between theimpulses of master'code, means for causing the feedback energy to be ofone polarity at times and to beof the other polarity at other times,

signaling means governed by said code followingl relay, and signalingmeans governed by said detector relays. Y

3. Ina coded railway signaling system, a sec-:- tion of railway track, aiii-st and a second-polarized detector-relay at'one end of said tracksection, a coding device having contacts continuously actuated between arst and a second position, the contacts of said coding device be-. ingeiiective when in their first position to conneci-l a source ofunidirectional energy across the rails of said vtrack sectionthrough thewindings of said detector relays so that an impulse of mas-v tercode-energy issupplied to the section rails and the contacts of saiddetector relays are caused to occupy their normal position, the con'-tacts of said coding device being effective when in their secondposition to connect said detector relays across said track rails in suchmanner that the contacts of one of said relays are moved to theirreverse position by energy of one polarity supplied over the track railsand so that the contacts of the other of said relays are moved to theirreverse position by energy of the other polarity supplied over saidtrack rails, a code following track relay at the end of said tracksection remote from said detector relays and'operated by master codeenergy supplied over the section rails, means associated withfsaidtrackV relay for supplying impulses of feed-back energy to said trackrails in the intervals between the `impulses ofA master code, means forcausing the feed-back energy to be of one polarity at times and to be ofthe other polarity at other times, signaling means governed by saidtrack relay, and signaling means governed by said detector relays. Y

4.' In a coded signaling system, in combination,l

a pair ofconductors extending between a rst and a second location, afirst and a second codingdeviceandza first and a second polarized relayatf said .first location, each of saidcoding devices having contactsmovable between a rst vand la second position, a circuit effective whenthe con-v tacts of both .of said coding devices' are in their rstposition to connect a source of unidirectional current across saidconductors through the windings of saiddetector relays so Ithat en-`ergy supplied through said relay windings moves the relay contacts totheir normal-position, a circuit eiective when the contacts of'saidsecond coding device are in their second'position to con-r nect saiddetector relays across said conductors so that the contacts of'one ofsaid relays Yare moved to their reverse position by energy of one'polarity supplied over saidconductors and the contacts of the other ofvs-aid relays are moved to their reverse position by energy of the-otherl polarity supplied over said conductors, a code following relay atsaid-second location operated by ,energy supplied over said-.conductorsfroml said rst location, means at lsaid-second locationY I for supplyingenergy .to said conductors in the intervals between impulses of venergysupplied to said conductors at said'rst location, means for causing theenergy supplied tosaid yconductors at said second location to be of vonepolarityl attimes and of the otherv polarity at other times,l

second. position and for thereafter movingl the` contacts of the secondcoding device to their second position, whereby there is aitime.interval `between in-terruptionof thesupply of energy to said.conductors-at said first location and connection of saiddetector .relaysacross. said conductors. and energy storedv in thecircuit ofV saidconductors will be dissipated beforesaid detector relays are' connectedacross said conductors, signaling means governed. by said vcodefollowingrelay, and sig nalingmeans governed by said detector relays. i

.-5. `In a coded signaling system, .in combination, a pair of conductorsextending between a first and a second location, a first and asecondcoding device and .a first and a second polarized relay at saidfirstlocation, each V,ofsaid coding devices having contacts movablebetween aiirstV and a second position,:'means.for moving the contacts ofboth of said coding devices to their rst position and for moving thecontacts of the rst codingdevice 4to their second Aposition and forthereafter moving the'contactsof said second coding `device to theirsecond position, means effective .when the contacts of both of saidcoding. devices are in? their first .position to connecta source ofunidirectional current acrosssaid con'- ductors through the'windingsv ofsaid detector relaysrin series .so that energy supplied through thewindings `of said detector relays causes the relay contacts to occupy!their znormalposition, a circuit effective when the contacts ofSaidsecond coding device are inftheir second position yto connect said.detector relaysacross'said conduc-l tors so that the contacts of one ofsaid relays are moved to their reverse position by energy of onelpolarity Vsupplied oversaid conductors and the contacts of the otherrof'saidrelays are moved to .their -reverse position by energy of theother* polarity supplied over said conductors, a code following relay atthe second'location operatedI by energy supplied over said conductorsfrom the first location, meansat' the second location for supplyingenergy tof said conductors in the intervals `between thev impulses ofenergy supplied to the conductors at the rst location, means for causingthe energy supplied to said conductors at said second location to be ofone polarity at times and of the other polarity at other times,signaling means governed by said code following relay, and signalingmeans governed by said detector relays.

6. In a coded signaling system, in combination, a pair of conductorsextending between a first and a second location, a first and a secondcoding device and a first and a second polarized relay at said firstlocation, each of said coding devices having contacts movable between afirst and a second position, means for moving the contacts of both ofsaid coding devices to their rst position and for moving the contacts ofthe iirst coding device to their second position and for thereaftermoving the contacts of said second coding device to their secondposition, means effective when the contacts of both of said codingdevices are in their rst position to connect a source of unidirectionalcurrent across said conductors through the windings of said detectorrelays in multiple so that energy supplied through the windings of saiddetector relays causes the relay contacts to occupy their normalposition, a circuit eiiective when the contacts of said second codingdevice are in their second position to connect said detector relaysacross said conductors so that the contacts of one of said relays aremoved to their reverse position by energy of one polarity supplied oversaid conductors and the contacts of the other of said relays are movedto their: reverse .position .by energy lof .the other polarity .suppliedover .said conductors, .acode following vrelay at the second.locationoperated byienergysupplied .over said conductors fron the.rstlocation means. at the second. locationfor supplying energy .to saidconductors inthe intervals vbetween the impulsesof energy suppliedto'zthe .conductors at the first location, means' for. causing theenergy suppliedto' said conducl* torsat said second location to beofone'polarity at times andof the Votherfpolarity. at other tim'e`s,`-signaling means governed by said code following relay, 'and signalingmeansgoverned by said der.1 tector relays. A y f 7. Inl ak coded.railway signaling-system, a-sec-E tion of. railway track, a rstandasecond polar-- izeddetector relayatl one Yend of said track sec# tion,a coding device having contactscontinu' ously actuated between aiirst-and a second 'position, `the contacts `of said-coding devicebeing' effective when in their rst position' to connect a source oflunidirectional energy across lthe railsof said'track section throughlthe windings" of said detector relays in series so`that anfimpulse ofmaster code energyl isf supplied to the'se'cti'on' rails andthe contactsof said detector relays are caused to occupy their normal position, thecom" tacts ofsaid .coding Vdevice being effective when in their secondposition -to connect said detector relays across said track rails insuch manner thatI thezcontacts vo-one of said'relays 4are "movedl td'theirA reverse-positionby energy-of one polarity supplied overthe trackrails anclso thatthe con'I tacts of the-other ofsaid`relays are'movedto"their reverse position'by'fenergy'of the other.'l polarity supplied oversaid trackVV rails, a codev fol-Y lowing track relayfat the end of `saidtrack sec:-` tion remote fromsaid detector relays 'and operaLa-ted'bymaster code energy'suppliedover'the section rails, meansassociated with said track relay for supplying impulses'of feed-backenergy to said'track rails in the intervals'betweenthe impulses ofmaster code, means for causing the feed-back energy to be of onepolarity at times and to be of the other polarity at other times,signaling means governed by said track relay, and signaling meansgoverned by said detector relays.

8. In a coded railway signaling system, a section of railway track, afirst and a second polarized detector relay at one end of said tracksection, a. coding device having contacts continuously actuated betweena first and a second position, the contacts of said coding device beingeffective when in their rst position to connect a source ofunidirectional energy across the rails of said track section through thewindings of said detector relays in multiple so that an impulse ofmaster code energy is supplied to the section rails and the contacts ofsaid detector relays are caused to occupy their normal position, thecontacts of said coding device being effective when in their secondposition to connect said detector relays across said track rails in suchmanner that the contacts of one of said relays are moved to theiryreverse position by energy of one polarity supplied over the track railsand so that the contacts of the other of said relays are moved to theirreverse position by energy of the other polarity supplied over saidtrack rails, a code following track relay at the end of said tracksection remote from said detector relays and operated by master codeenergy supplied over the section rails, means associated with said trackrelay for supplying impulses of feed-back energy to said actuatedbetweenga first and a second position,`

the contacts of said coding device being effective when in their firstposition to connect a source of unidirectional energy across therails ofsaid track section so that an impulse of master code energy is suppliedto thesection rails, the.con tacts of said coding device also -beingeffective when in their first position to cause to be suppliedtowindingsof said detector relays energy eiective to cause the contactsofY said detector relays to occupy their normal position, the contactsof said coding device being eiective when in their second position tovconnect said detector relays across said track rails in such manner thatthe contacts of one of said relays are moved to their reverse positionby energy of one polarity supplied over the track rails and lso that thecontacts of the other of said relays are moved to their reverse positionby energy of the vother polarity supplied over said track rails, a codefollowing track relay at the end of said track section remote from saiddetector relays and operated by master code energy supplied over thebsection rails, means associated with said track relay for supplyingimpulses of feed-back energy to said track rails in the-intervalsbetween the impulses of master code, means for causing the feed-backenergy to be of one polarity at times and to be of the otherpolarity atother times, signaling means governed by said track relay, and signalingmeans governed by said detector relays.

, 10. In a coded railway Vsignaling system, in

combination, a first anda second coding devic and a first and a secondpolarized detector relay at one end of said track section, each of saidcoding devices having contacts movable between .a rst and a secondposition, means riormoving the contacts of both of said coding devicesto their irst position and for moving the-contacts of the iirst codingdevice to their second .-position and for thereafter moving the contactsof said second coding device to. their second position, means effectivewhen the contacts of both of said coding devices are in their firstposition to connect a source of unidirectional energy across the railsof said tracksection so that animpulse of master code is supplied tothesection rails, means eiective when the contacts ofy 'both of saidcoding devices are in their first position to cause Y to'be supplied towindings of said detector relays energy effective to cause vthe contactsof said de.- tector relays .to occupy their normal positions.

means effective when the 'contacts of said coding devices are intheir-second position to connect said detector relays acrossy the trackrails in such manner that the contacts of one of said relays are movedto' their reverse position vby Y energy of one polarity supplied overthe track rails and so that the contacts :of the other of said ree laysare moved to their reverse positionby energy of the other polaritysupplied Aover saidftrack rails;

a code following track relay at the end of said track section remotefrom said detector relays andV operated by master code energy suppliedover the section rails, means associated with said track relay forsupplying impulses of feed-back energy to. said track rails in theintervals between the impulses of master code, means for causing-thefeed-

